1. Field of the Invention
The present invention relates to a control system for a vehicle with an automatic transmission which simultaneously controls an air-fuel ratio of an engine of the vehicle and shifting in the automatic transmission.
2. Description of the Prior Art
This type of control device has been proposed by Laid-Open Japanese Patent No. 59-134338, such control device being adapted to store in a memory a first shift pattern with an importance attached to output and a second shift pattern with an importance attached to fuel economy. Also stored in the memory are a first value of fuel enrichment corresponding to the first shift pattern and a second value of fuel enrichment corresponding to the second shift pattern, such that when the first shift pattern is selected, the shifting in the automatic transmission is controlled in accordance with the first shift pattern and at the same time the air-fuel ratio of the engine is controlled in accordance with the first value of fuel enrichment, and also that when the second shift pattern is selected, the automatic transmission is controlled in accordance with the second shift pattern and at the same time the air-fuel ratio of the engine is controlled in accordance with the second value of fuel enrichment.
This fuel enrichment at this time takes place within a high-speed range and within a high-load range where the flow rate of exhaust gases increases, gaining an effect of restraining a temperature rise of an exhaust system including an exhaust catalyst.
Therefore, selecting a shift pattern with an importance attached to fuel economy can improve the fuel economy by leaning out the air-fuel mixture, and also selecting a shift pattern with an importance attached to output can obtain sufficient output.
In the control device of the above-described arrangement, however, as a selector switch is used for the selection of the shift pattern with an importance attached to fuel economy as well as the shift pattern with an importance attached to the output, the operation of the selector switch will be complicated for a driver who wants some more acceleration force for a brief period of time (for example when accelerating for entering a super-highway or for passing another vehicle) during vehicle operation using the shift pattern with an importance attached to fuel economy. During this period of acceleration, therefore, it is very likely that acceleration is done by the use of the shift pattern with an importance attached to fuel economy.
In the shift pattern with an importance attached to fuel economy, an upshift line or position is set low. Therefore, an upshift is made into a gear on the high-speed side (i.e. to a higher gear) while the vehicle speed is still relatively low, and the accelerator pedal must be depressed substantially to obtain a sufficient acceleration force. Accordingly, the engine will be operated under a great load, and will require fuel enrichment, resulting in lowered fuel economy.
Automatically changing only the shift pattern over to another pattern with an importance attached to output, at the time of acceleration, will also increase the amount of fuel in the high-speed range of the engine, similarly resulting in lowered fuel economy.
This problem will happen not only in the above-described finitely variable automatic transmissions but also in infinitely variable transmissions.